Note that there are always two possible angles between two lines, depending in which direction the angle is measured: a smaller one and a larger one. The sum of the two possible angles is of course always 360 degrees (full circle).

The angle between your lines is 160 degrees (smaller angle) but it is also 200 degrees (larger angle)

Which angle QCAD measures depends on the cursor position while clicking the second line. If the cursor is inside the smaller angle, the smaller angle is measured.

Thanks Andrew,
I tried placing the cursor on both sides, near and far from the lines and I am getting the same results. Measuring from the top line to the adjacent line right, I get 160. The same op from the line left of top to the top line, it is 200. It seems to make no difference where I place the cursor.

The behavior I have described applies for the latest QCAD version only (2.2.2.0). In previous versions, the order in which you click the lines determined which one of the two possible angles is measured (counter-clockwise angle measurement).

QCAD 2.2.2.0 also shows you the angle that is measured as preview in the drawing.